Diaphragm drive



Jan. 17, 1928. 1,58,832

H. c. HARRISON DIAPHRAGM DRIVE Original Filed July 31, 1925 Patented Jan. 17, 1928.

UNITED STATES PATENT OFFICE.

- HENRY C. HARRISON, OF PORT WASHINGTON, NEW YORK, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

DIAPHRAGM DRIVE.

Application filed July 31, 1923, Serial No. 654,915. Renewed June 4, 1927.

an electrical system. The inductance L, the

capacity C and the resistance R of the'electrical system have their respective counter parts in the mechanical field, namely, mass M for inductance; the reciprocal of the elasticity, for the capacity; and r for the mechanical resistance. The characteristic impedance of a mechanical transmission system having an appreciable amount of elasticity S, as well as mass M per section equals, for small energy dissipations in the transmission system,

frequency, and

l S M is called the cutoff frequency and is the frequency at which the impedance of the transmission line becomes very high and hence substantially cuts ofi transmission. The

represents the velocity of wave transmission in sections per second, along such a line.

According to the present invention, the impedance of (1) the moving parts of the driving motor, (2) the diaphragm, and (3) the mechanical transmission system connecting the motor and the diaphragm, are so chosen that the transition losses of the transmitted sound waves is small.

In case the value of the impedance (1) is substantially equal to that of (2), then the impedance of the "mechanical transmission system connecting (1 and (2) should have the same value as (1 and (2). If, on the are independently other hand, the impedance of 1) is different from that of (2 then the impedance of the drive should taper from the impedance of 1) to that of (2), that is, the following impedance relation should exist: Q Z, Z, Z 1

a constant where Z is the characteristic mechanical impedance of the diaphragm and the attachments thereto, Z the impedance of the first section of the mechanical line, Z, the impedance of the second section, Z 1 the impedance of the last section, and Z the impedance of the moving parts of the driving motor. This arrangement will, therefore, function as'a mechanical transformer for coupling the two unequal impedances.

Another phase of the invention relates to the use of large diaphragms composed of mechanically weak material, such as paper, which forms an eflicient coupling with the air, and has for an object to provide a drive the weight of which is not effectively added to the weight of the diaphragm, which, therefore maintains a mechanical which is small and of the order of that of the surrounding air in which it works. This segregation of the weights of the drive and diaphragm is accomplished by providing an elastic coupling between them whereby they vibratile. The driving means preferably also complies with the requirements previously set forth.

Referring to the drawings, Fig. 1 is a sectional view on line 11, Fig. 2, of the diaphragm and its drive. Fig. 2 is a view in elevation.

Referring in detail to Fig. 1, the electromagnetic drive 1, may be of the type shown and described in detail in Egerton Patent No. 1,365,898, January '18, 1921. This drive comprises a rod 2 which reciprocates in accordance with the electric currents supplied to the electromagnetic drive 1. The rod 2 is connected to the center of a reed 3 shown in the plan View in Fig. 2, and which has three equi-distant laterally extending arms 4. Near the end of each of the arms 4 is suitably fastened a pin tened in any suitable manner to the center of areed 6, each of which has three laterally extending arms 7 similar to arms 4. Each of 5, each of which is fasimpedance the arms? is suitably fastened, for instance,

means of a pin 8 to a point on thediab phragm 9.

i The reeds 3 and 6 may be of any suitable material such as steel, aluminum, or the hire.

The diaphragm 9 may be a foot or more in diameter. In the form shown, phragm has its periphery clamped between and supported by the rings 10, 11 fastened by bolts 12 and suitably supported, for instance, in an upright position by thebase 13 to which ,ring is fastened by bolts 14. The ring 10 has supporting arms 15, 16, 17 which terminate nearthe axis of the ring in a circular member 18 which has bolted thereto (bolts the casing 19 which contains the driving motor 1. I The opening in the ring 18 maybe closed by the cover 21 which is also fastened by the bolts 20.

In assembling the device, the diaphragm with the reeds and pin 2 fastened thereto, is moved into position against ring 10 and then ring 11 is fastened on. The drive 1, carried bycasing 19 by means of screws such as 22,

4 is moved into position and pin 2, which is threaded, is fastened to pin 23 of the drive by the lock nuts 24 and 25.

If the impedance of the moving parts of the motor 1 about equals that-of the dia-- phra In 9, the masses of the reeds, the pins and t e diaphragm should be such that equal masses are found on opposite sides of the three lines and the reeds 3, 4, 6 and 7 should have a substantial amount of elasticity such as inherent in thin steel, aluminum, or the like, thereby avoiding. transition losses. If the impedance of the moving parts of the motor 1 is diiferent from that of the diaphragm and its attachments, (the pins 8), the mass and elasticity of each section of the drive should be so chosen as to taper the impedance between the 'motor and the diaphragm as above set forth, i. e., the mass and elasticity should increase from section to section as the terminus ,(motor or diaphragm) of greater impedance is gpqproac e ile the invention has been described in connection with a telephone-receiver, it is equally applicable to a transmitter, phonograph or the like.

What' is claimed is 1. A large direct acting diaphragm, a motor element therefor, and means connected to said motor element for driving substantially all points of said diaphragm in phase, the masses and elasticities, from an im edance standpoint, being separated from t e diaphragm.

this dia- 1 AA, B-B and 0-0 in Fig. 1,

' 2. Aphonie diaphragm, an'da drive there.-

for'wh-ich varies along its length in mechanical-impedance. v

3 3. The method which comprises progressively varying the mechanical impedance of a drive between a motor and a diaphragm. I 4. An acoustic device comprising a diaphragm constituting a portion of a. mechanical line and a driving means therefor constituting a second ortion of said line, the second portion oft e line being divided into a lurality of lines in parallel having a total impedance equalto that of the main line,

whereby the diaphragm is driven at a number of points in phase.

5. An acoustic device comprising '9. dia- .phragm constituting a cal line and a driving tuting a second portion of said line, the second. portion at the diaphragm consisting of a multiple of parallel branches the number of said branches progressively decreasing from {he diaphragm section by section to a single. ine.

6. An acoustic device comprisin a diaphra'gm constituting a portion of a mechanical line and a drivin means therefor constiportion of a mechanimeans therefor con'st1- tuting a second portlon of said line, the second portion at the diaphragm consisting of a multiple of parallel branches, the number of said branches progressively decreasing from the diaphragm section by section to a single line'the sum of the impedances of the lines progressively varying from the diaphragm to the single line.

7 An acoustic device comprising a diaphragm constituting a portion of a mechanical line and a driving means therefor constituting a second portion of said line, the driving means progressively varying-along its length in mechanical impedance, the effecfrom an frequencies whereby the diaphragm is driven at a number of points in phase.

In witness whereof, I hereunto subscribemy name this 2"lfiiylof July A. D., 1923.

BY G. HARRISON.

III 

